1. Field of the Invention
The present invention relates to a control apparatus for controlling a space robot for use in an assembling operation, repairing or servicing operation, etc., in a space environment.
2. Description of the Related Art
A flying target can very readily be captured by controlling a ground-based robot as well known in the art. The ground-based robot will be explained below in connection with its control system by referring to FIG. 1.
The capturing of a target by the ground-based robot will be explained below.
As shown in FIG. 1, the ground-based robot recognizes the position and attitude of the target by a visual sensor. A result of recognition is input to a manipulator trajectory generator 2 where a trajectory from a present position of a manipulator to a capturing position of the target is set. The manipulator trajectory generator 2 computes a desired position of a manipulator in the robot body coordinate (.SIGMA..sub.C) and delivers the sequential target position .sup.c Pm.sup.d, as sequential data, to a manipulator forward end velocity generator 3 where the manipulator tip velocity command value .sup.c Vm.sup.d is found.
Then the velocity command value .sup.c Vm.sup.d, together with a Jacobian matrix J found by a Jacobian matrix generator 4 with the use of a manipulator rotational angle, is supplied to a manipulator rotational velocity generator 5 where the manipulator rotational velocity .omega.c.sup.d is computed. Based on a result of the computation the manipulator is moved to the target capturing position and a gripper grips or captures the target by its closing operation.
As set out above, the ground-based robot can readily capture the target.
For a space robot having a manipulator mounted on an artificial satellite, a control system adopted on the ground cannot be employed directly because the space robot on the satellite and a flying target to be captured are moved, while floating in the gravitationless space. The reason for this is as follows.
When the manipulator is operated in space, since the satellite having the base of the manipulator is oscillated in position and attitude due to a reaction force according to this operation, thus making it difficult to locate the tip of the manipulator. If the same position control system and velocity control system as those on the ground are employed upon the capturing of the flying target, by a gripper on the tip of the manipulator, which is floatingly moved in space, then the manipulator is oscillated due to a load involved and there is a possibility that an excessive load will act on the manipulator or a gripping target will be released out of the gripper of the manipulator. Further, if the gripper on the tip of the manipulator collides with the target flying in space, translational and rotational motions act on the flying target, causing the target to be moved outside an operation range of the manipulator, and hence, moved out of a capturing or gripping range.
As set out above, if the control system adopted on the ground-based robot is employed on the space robot, it is impossible to better capture or grip the target floatingly moving in a specific environment, that is, in a space environment. Therefore, there is a growing demand for a control system applicable to the space robot.
The document relating to the present invention includes Published Unexamined Japanese Patent Application 4-57683, N. Kubota et al., "Compensation Control of Free Flying Space Robot Using Sensors", Poc. of the 9th Conference of the Robotics Society of Japan, Nov. 27 to 29, 1991, pp. 101-102 and N. Kubota et al., "Control of Flying Robot for Capturing Maneuver", Proc. of Dynamics and Design Conference, Jul. 9-11, 1991, pp. 387-392. However, no practical method for operating the arm of the space robot through the utilization of the sensors is shown in the document above.